JHZR2:
Despite not having the latest and greatest, I still think that you'll feel an improvement from good tires. For instance, braking is braking and in virtually all cars it is limited by tire grip. Furthermore tire design can influence braking distance even when lock up isn't involved. Any snow tire I have ever installed significantly increases braking distance even when well below lockup thresholds. The same can hold true when comparing between all-seasons, depending on just what the difference is between them.
I have a 1998 BMW 528 with MT and sport suspension. It's not an M car, it's pretty big and relatively heavy, not all that fast in a straight line and not nimble like an e30 "go kart" (reference from earlier in the thread). Despite all this, I put UHP summer tires on and can absolutely, without a doubt, every-minute-of-the-day feel a positive improvement over even high performance all seasons (like Michelin Pilot Sport A/S). I can even feel subtle differences between different types of UHP summer tires (Dunlop 2000E, Toyo T1-S, Toyo T1R and now my current PS2s). If better tires only made a difference in the best sports cars this wouldn't be the case.
Now, as long as I keep bushings, ball joints and shocks in good shape it handles pretty well and although it isn't a true sports car I feel it isn't a waste of UHP tires. With confidence-inspiring stick and excellent road condition communication I can really toss it into twisties when I have the opportunity and braking is great. There is also one particular emergency high speed accident avoidance maneuver I executed (with the Toyo T1Rs installed) that I am not sure I would have pulled off without UHP tires (seriously). It saved our bacon and potential totaling of the car.
There's another thread in here about whether Michelins are always better than other brands. IMO, Michelin seems to be "often" better than other brands but they make some lemons too. If you've done your research and the Michelins you're looking at are some of the "good" ones, then I would personally go for the Michelins over the Kuhmos. I'm not a Michelin fanboy - these PS2s are the first Michelins I've bought in 15 years. My dad always buys Michelins though.
Over the years I've seen lots of people give Kuhmos good reviews (sometimes to their surprise), or post after only 1000miles and say they love them and will never spend big bucks on tires again. Unfortunately a lot of times their pleasure doesn't last. You hear from a LOT fewer Kuhmo owners who got long tread life and were pleased from "cradle to grave" with their choice. Sure, they're out there, but in much lower numbers than owners who became displeased.
